1. Technical Field
The present invention relates to a donor-acceptor conjugated polymer and an organic electronic device including the same.
2. Description of the Related Art
Organic electronic devices such as organic thin film transistors, light emitting diodes, solar cells, and memories have attracted great attention in relation to future application to flexible devices by virtue of ease of manufacture/processing, low cost, flexibility, extensibility, printability, and the like. In particular, an organic memory has been studied on application to data storage media for flexible devices. Various polymers, such as polythiophene, polyaniline, polyvinylcarbazole, and polyimide have been generally used as a polymer electrolyte or a matrix in a doping system or a mixing system. As part of an effort to improve memory effects, several research groups introduced organic nanoparticles or carbon nanomaterials (carbon nanotubes, graphene, or fullerene) into a polymer matrix to enhance switching properties (write-once-read-many properties, unipolar or bipolar switching) and memory performance. However, it is difficult to achieve uniform dispersion of nanoscale particles in a polymer due to agglomeration of ions which can cause deterioration in memory performance.
Recently, it has been confirmed that a donor-acceptor-based polymer system having an aliphatic hydrocarbon backbone, such as a block copolymer of poly(9-(4-vinylphenyl)carbazole) (electron donor) and poly(2-vinylpyridine) (electron acceptor) or a fullerene (electron acceptor) end-capped poly(2-(N-carbazolyl)-ethyl methacrylate) (electron donor), exhibits excellent non-volatile memory performance. In addition, there was a study on applicability of a polymer, which has both donor and acceptor parts within a repeat unit and exhibits excellent dimensional stability, to non-volatile memory devices. A donor-acceptor (D-A) conjugated polymer allows electron transition between a ground state and an excited state, required for an active layer of memory devices, and effectively prevents agglomeration of ions to allow formation of a uniform thin film, thereby considerably improving performance of the device. In such a D-A conjugated polymer system, it is possible to control electric charge transfer between the donor part and the acceptor part through strength and arrangement of donor and acceptor materials, which plays an important role in enhancement of electrically bi-stable switching behavior. Chen, et al., succeeded in preparation of a D-A conjugated polymer composed of selenophene and 3,6-dithiophene-2-yl-2,5-dialkylpyrrolo[3,4-c]pyrrole-1,4-dione, which exhibits transistor type non-volatile memory properties due to the film morphology and the ambipolar nature of polymers. A resistive memory is a 2-terminal device having a simple sandwich structure of metal/insulator/metal (MIM), whereas a transistor type memory is a 3-terminal device. Elimination of a need for transistors has an advantage in terms of reduction in manufacturing costs. In addition, few polymers exhibit both memory effects and environmental stability. For actual application, these problems must be overcome.